"One Pot" Synthesis Of Hydrocarbon Esters And Hydrocarbon Alcohols Mediated By Zinc Under Solvent-free Conditions

In recent years, with the rapidly emerging and development of green chemistry, environmentally friendly-economics have become an important impetus of technology innovator, and make green organic synthesis face serious challenge. Developing more benign synthetic procedures in chemical synthesis is important in moving towards sustainable technologies. In reducing the amount of waste, energy usage, and the use of volatile, toxic and flammable solvents, several approaches are available including avoiding the use of organic solvents for the reaction media. Replacement media include non-volatile and recyclable ionic liquids, H₂O, supercritical CO₂, polyethylene and polypropylene glycol. An alternative approach avoids the use of a reaction medium as the so-called 'solvent free' or 'solventless' reaction.Being important building blocks and versatile synthons, homoallylic and homopropargyl alcohols are highly featured in the organic syntheses of many biological active molecules such as macrolides, polyhydroxylated natural products, and polyether antibiotics. In a long synthetic scheme it may be desirable to protect the newly generated free alcohol before proceeding further. It would be more advantageous if both addition and acetylation reactions are achieved in one pot. One pot synthesis saves steps by eliminating the need to isolate the intermediate and thus minimizes waste.Benzylation of carbonyl compounds is one of most useful processes in organic synthesis. Usually, this type of reaction is performed in anhydrous organic solvent. Since the 1980s, the importance of organic reactions carried out in aqueous media has been gradually recognized because there is growing public interest in green chemistry. Allylation and propargylation of carbonyl compounds have been extensively studied. Surprisingly, benzylation of carbonyl compounds has not been the topic of much interest.From the view of environmentally friendly, this thesis achieved the solvent-free synthesis of homoallyl , homopropargyl estres andβ-acetoxyl esters through zinc or zinc copper couple mediated one-pot reaction. At the same time, the benzylation of aromatic aldehydes was investigated under solvent-free conditions. This thesis includes three chapters.Chapter one: Recent Development of Green Reaction Mediated by Metal ZincIn this section, zinc-mediated green organic reaction of addition, coupling, reduction and elimination under aqueous, supercritical liquids, ionic liquids and solvent-free conditions were reviewed. In particular, zinc mediated addition reaction in aqueous media were summarized in detail.Chapter two: Environmentally Friendly Three Component "One-pot" Synthesis of Hydrocarbon Esters Mediated by Metal ZincThis chapter mainly investigated three component one pot synthesis of hydrocarbon esters mediated by zinc powder or zinc copper couple under solvent-free conditions.We firstly achieved the homoallyl esters, homopropargyl esters andβ-acetoxyl esters mediated by Zn/Zn-Cu under solvent-free conditions. Compared with literature methods, the valuable features of our methodology include: (i) shorter reaction time and higher yield: in particular, good yields were achieved mediated by zinc copper couple. (ii)no catalyst, one-pot and solvent-free. (iii) broader substrate scope: our methods are applicable to both aliphatic and aromatic aldehydes. More importantly, we find that our method can be applicable to propargyl bromide and a-bromoacetic esters.Chapter three: Zinc-mediated Benzylation of Aromatic Aldehydes under Solvent-free ConditionsBenzylation of carbonyl compounds by benzyl halides, mediated by metals, to produce 1,2-diaryl alcohols is one of the most useful processes in organic synthesis because of the great potential for 1,2-diaryl alcohols to be converted to important building blochs in natural product synthesis. In this section, we firstly realized benzylation of aromatic aldehydes mediated by zinc powder under solvent-free conditions. Compared with literature methods, the advantages of our methodology are higher yieldes, environmentally benign and no catalyst. Reduction and coupling products were not observed.